Browsing by Author "Becker, Bruce"

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    Development of a high-level trigger for the dimuon spectrometer of the ALICE experiment at the large hadron collider
    (2006) Becker, Bruce; Vilakazi, Zeblon; Cleymans, Jean
    The ALICE experiment at CERN's Large Hadronic Collider will mark the beginning of a new phase in the study of ultra-relativistic heavy ion-collisions. It will be possible to explore in great detail phenomena discovered or hinted at in the course of experiments at the Relativistic Heavy Ion Collider, in particular the signals of the quark-gluon plasma. One of the most promising signals of the creation of this new state of matter is the anomalous suppression of the Υ (bb) and J/v(cc) families. One of the main decay channels of these mesons is into dimuons and ALICE has a dedicated dimuon spectrometer in order to study the spectra of these interesting particles. The signal is, however, swamped by a large background from several other muonic sources. Due to the large data rate expected for ALICE and the limited bandwidth, a highly efficient and selective trigger is required for the experiment - the dimuon high-level trigger (dHLT). This thesis concerns the context, development and implementation of the ALICE dimuon high-level trigger. The physics context ot the experimentation is described, as well as the technical requirements of the system. The performance of the prototype is investigated with the use of Monte-Carlo simulations. An investigation into the performance estimates of system in the expected physics environment was performed, which validated the benchmarks, as well as investigation of the effect of possible modifications of quarkonia yields due to QGP formation on the response of the dHLT.
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    Investigation of heavy ion reaction mechanisms by means of the inclusive 93Nb(12C,7Be) and 93Nb(12C,9Be) reactions
    (2002) Becker, Bruce
    Inclusive continuum cross-sections for the reactions 93Nb(12C,7Be) and 93Nb(12C,9Be) were measured at the NAC using a ΔE - E setup. A theoretical light output model which could account for the mass and charge dependance of the NaI E detectors was employed to calibrate the NaI(TI) detectors. The model is outlined and it is shown that the nonlinearity of the detector response is only due to a term which describes the mass-dependance. Investigation of the cross-sections revealed interesting facts about the dominant reaction mechanisms in the interaction of 120 with heavy targets. A theoretical model developed by the Milano group has been very successful in describing the continuum cross-sections of a particles (including 9Be) created in similar reactions of 120 and 160, incident on heavy targets. The analysis shows that the same description of the continuum cross-sections of 7Be and 9Be gives good agreement with the data (with different energy-loss parameters and survival probabilities), although there are discrepancies, especially at the lower incident angles. These small discrepancies may indicate the presence of a multistep direct reaction between the detected fragment and the residual nucleus in the exit channel. The most notable result of the analysis of the data was that the spectra of 7Be and 9Be, previously suspected to be created in a final-state interaction of sBe with the residual nucleus, are well-described by a friction-dissipative breakup mechanism.